Aaron Wilkosz

Optical branching in dye-doped polymeric waveguide

We demonstrate theoretically and experimentally that a single optical beam splits into multiple beams (branches) as a result of light induced permanent refractive index decrease in a dye-doped polymeric slab waveguide upon its upconverted photobleaching. The input Gaussian beam initially splits into two primary branches that grow in time moving out of the central axis and eventually collapse into numerous secondary branches. The proposed theoretical model is nonlocal in time and is based on a Shrodinger-type nonlinear propagation equation complemented by a rate equation for the decrease of the refractive index.

Optical channel waveguides formed by upconverted photobleaching of dye-doped polymer film in regime of dark spatial soliton

We demonstrate theoretically and experimentally that an initially Gaussian optical beam (633 nm wavelength) sent through a π-step phase mask and launched into a thin film of polymer poly(methyl methacrylate) doped with laser dye 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)4H-pyran known as DCM evolves into a spatial structure similar to a dark spatial soliton. This takes place due to nonlinear mechanism of upconverted photobleaching of the dye-doped polymer. The result of beam structuring is the formation of a permanent pattern of the refractive index of the film that acts as a channel waveguide trapping a weak Gaussian probe beam coaxial with the main beam. The proposed theoretical model is nonlocal in time and is based on a Schrodinger-type nonlinear propagation equation for the main beam and a linear propagation equation for the probe beam complemented by a rate equation for the light-induced decrease of the refractive index.

Dark spatial solitons in photopolymer films for optical interconnections

We demonstrate theoretically and experimentally that an initially Gaussian red light beam sent through a ?step phase mask and launched into a thin film of polymer poly(methyl methacrylate) doped with laser dye 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)4H- pyran known as DCM evolves into a spatial structure similar to a dark spatial soliton. This takes place due to the Kerr-type time-delayed nonlinearity associated with the mechanism of up-converted photobleaching of the dye-doped polymer. The proposed theoretical model is nonlocal in time and is based on the Shrodinger-type nonlinear equation for the amplitude of the propagating beam complemented by the rate equation for the light-induced decrease of the refractive index. The result of the structuring of the beam is the formation of a permanent pattern of the refractive index of the film that acts as a channel waveguide, trapping a weak Gaussian probe beam close to it. The probe beam can propagate along or against the soliton. We also demonstrate the tolerance of trapping to a possible shift or tilt of the probe beam with respect to the soliton. This makes the proposed approach potentially useful for interconnections between individual fibers, fiber ribbons, bundles, and multicore fibers as well as between fibers and planar integrated optical devices.

Nonlinear optical waveguides based on polymeric films doped with phthalocyanines

The results are reported on the study of nonlinear optical properties of poly(methyl methacrylate) waveguides doped with 2,9,16,23-Tetrakis(phenylthio)-29H,31H- phthalocyanine. Polymeric host provides acceptable waveguide quality that is hardly achievable for phthalocyanine monocrystaline films or glasses. In comparison with ordinary materials such as lead-phthalocyanine, 2,9,16,23-Tetrakis(phenylthio)-29H,31H- phthalocyanine shows better solubility and is less affected by polymeric matrix. It preserves strong absorption in visible region with single peak at 627 nm. Third order nonlinearity of phthalocyanine doped polymer was studied with Z-scan and degenerate four wave mixing techniques, and also with waveguide mode spectroscopy based on prism coupling. Slow thermal component of third order susceptibility was measured using cw Ar+ laser (514 nm line) in the spectral region out of the absorption band, and He-Ne laser (633 nm line) inside the absorption band. In the latter case nonlinear refractive index was minus 1.87 multiplied by 10-2 cm2/W providing strong shift of waveguide modes to the region of low indices where light confinement might no longer be achieved. Transient and fast third order susceptibility is studied using nanosecond and picosecond pulses from frequency doubled Nd:YAG laser at pump power up to 100 MW/cm(superscript 2

Optical properties of metallophthalocyanines in solution and in a sol-gel matrix

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Nonlinear propagation of an optical beam in dye-doped polymeric waveguide with photobleaching

The sol-gel method is convenient for preparing amorphous transparent oxides with a wide range of optical properties including laser action, optical gain, phosphorescence, SHG and other non-linear effects. The sol-gel method was used to produce sol-gel samples using metallophthalocyanines. From metallophthalocyanines we used Cu (II) phthalocyanine (beta) - form, Ni (II) phthalocyaninetetrasulfonic acid, tetrasodium salt, Cu (II) 3,10,17,24-tetra-tert-butyl-1,8,15,22-tetrakis (dimethylamino)-29H, 31H-phthalocyanine, Zn 1,4,8,11,15,18,22,25-octabutoxy- 29H,31H-phthalocyanine Ni (II) 5,9,14,18,23,27,32,36-octabutoxy- 2,3-napthalocyanine and Cu (II) 5,9,14,18,23,27,32,36-octabutoxy-2,3-napthalocyanine. In our paper we report and discuss the results obtained from the measurements of the index of refraction using the prism coupling technique, absorption spectra and non-linear transmission measurements using picosecond laser pulses. The absorption spectras of Cu, Zn and Ni phthalocyanines in solution and sol-gel matrix showed decomposition. We found optical limiting after 0.2 J/cm2 in Ni (II) phthalocyaninetetrasulfonic acid, tetrasodium salt solution; glass samples showed no optical limiting. The mean of the index of refraction measured for all the (beta) -Cu phthalocyanine samples was 1.42. No birefringency was found.

Fully optical light beam steering in dye-doped polymer films with time-delayed third-order nonlinearity associated with upconverted photobleaching

We report on single optical beam splitting into several beams (the optical branching effect) in a single mode slab waveguide made from poly(methyl methacrylate) (PMMA) doped with dye 4-(Dicyanomethylene)-2-methyl-6-(pdimethylaminostyryl) 4H-pyran known as DCM. The effect is associated with permanent refractive index decrease accompanying upconverted dye photobleaching. Unlike the defocusing Kerr effect, the refractive index response to the optical field is nonlocal in time for the index depends on the absorbed energy instead ofthe instant light intensity. The effect therefore takes place at much lower power then nonlinear propagation effects in Kerr media (less than 1 kW/cm2 ).The proposed model of branching uses soliton-like solutions of Shrodinger-type nolmear propagation equation complemented by the rate equation for the refractive index change. Computer simulations based on the model demonstrate all the effects observed experimentally such as beam splitting into two primary side branches followed by their collapse into multiple secondary branches.

Time delayed beam splitting in nonlinear polymeric waveguides induced by low power upconverted photobleaching

We demonstrate theoretically and experimentally that initially Gaussian optical beam sent through the (pi) -step phase mask and launched into a thin film of polymer poly(methyl methacrylate) doped with laser dye 4- (Dicyanomethylene)-2-methyl-6-(p-dimethylaminostryl(4H-pyran known as DCM evolves into a spatial structure similar to the dark spatial soliton. This takes place due to the third order nonlinearity associated with the mechanism of unconverted photobleaching of the dye-doped polymer. The result of the structuring of the beam is the formation of a permanent pattern of the refractive index of the film that acts as a channel waveguide trapping a weak Gaussian probe beam coaxial with the main beam. We also demonstrate theoretically the possibility of trapping the probe beam, which propagates in opposite direction at an angle to the main beam. The proposed theoretical model is nonlocal in time and is based on the Shrodinger-type nonlinear propagation equation for the main beam and the propagation equation for the probe beam complemented by the rate equation for the light-induced decrease of the refractive index. The results of this study can find application in optical interconnects and data processing.

Upconverted photobleaching and nonlinear effects of optical beam self-action in dye-doped polymer waveguides

We present theoretical and experimental data and discusses a theoretical model developed to study optical beam splitting induced by photobleaching a dye-doped polymeric waveguide, where instant refractive index reaction to light intensity redistribution is replaced by permanent index decrease associated with dye photobleaching.

Optical beam splitting in a nonlinear polymer waveguide

We report on optical beam self-action in a waveguide made of poly(methyl methacrylate) doped with laser dye DCM upon its upconverted photobleaching produced by radiation of a low power CW He-Ne laser. Nonlinear effects of self-action produce spatially stable beam structures usually interpreted as dark spatial solitons in media with negative Kerr-like nonlinearity. We demonstrate experimentally that the proposed mechanism of self-action is more likely upconverted photobleaching, i.e. photobleaching by short wavelength radiation resulting from frequency upconversion of the primary red laser light. Upconversion is not a multi-photon process. It possibly occurs as a result of inhomogeneous line broadening and excitation of thermally populated higher vibrational energy states in the ground state of the dye molecules. Theoretical model of beam propagation is based on the Shrodinger-type nonlinear propagation equation complemented by the rate equation for photobleaching. The result of simulations are in good agreement with experimental data. Possible applications of the studied effects include photonic switching and optical interconnects.